(a) Field of the Invention
The present invention relates to a liquid crystal display (“LCD”) and a driving method thereof. More particularly, the present invention relates to an LCD having an improved response speed of liquid crystal (“LC”) molecules therein, and a driving method of the LCD.
(b) Description of Related Art
A liquid crystal display (“LCD”) is one of the most widely used flat panel displays. An LCD includes two opposed panels provided with field-generating electrodes such as pixel electrodes and a common electrode, and a liquid crystal (“LC”) layer interposed between the two panels. The LCD displays images by applying voltages to the field-generating electrodes to generate an electric field in the LC layer, which determines orientations of LC molecules in the LC layer to adjust polarization of incident light.
Among the LCDs, a vertical alignment (“VA”) mode LCD, which aligns LC molecules such that the long axes of the LC molecules are perpendicular to the panels in the absence of an electric field, is often employed because of its high contrast ratio and wide reference viewing angle, which is defined as a viewing angle making a contrast ratio equal to 1:10 or as a limit angle for the inversion of luminance between the grays.
The wide viewing angle of the VA mode LCD can be realized by cutouts and/or protrusions on the field-generating electrodes. Since the cutouts and the protrusions can determine the tilt directions of the LC molecules, the tilt directions can be distributed into several directions by using the cutouts and the protrusions such that the reference viewing angle is widened. A patterned vertically aligned (“PVA”) mode LCD using the cutouts may substitute an in-plane switching (“IPS”) mode LCD, and is thereby recognized as a wide viewing angle technology.
Meanwhile, the LCD is widely used for television sets as well as for display devices for computers, and it is necessary to display a moving image. However, since the response speed of the LC molecules is slow, it is difficult for the LCD to display the moving image.
Due to the slow response speed of the LC molecules, until a voltage charged in an LC capacitor reaches a target voltage, that is, a voltage capable of obtaining a desired luminance, an amount of time is required. The amount of time is varied based on the previous charged voltage of the LC capacitor. Thus, when a difference between the target voltage and the previous charged voltage is large, the voltage charged in the LC capacitor does not reach the target voltage for one frame after application of a data voltage corresponding to the target voltage.
Thus, to shorten the time for reaching the target voltage, a dynamic capacitance compensation (“DCC”) method has been proposed. The DCC method uses the fact that the response speed of the LC molecules increases as a voltage applied across both ends of the LC capacitor becomes larger.
A data voltage applied to a corresponding pixel (although a difference exists between the data voltage and the common voltage, for convenience the common voltage is assumed as “0”), which is higher than a target voltage is applied, to shorten the time for reaching the target voltage.
However, to use the DCC method, a frame memory is necessary for storing image signals for one or two frame, and thereby the manufacturing cost is increased.